Ear insert hearing aid



Feb. 7, 1961 H. M. BUSSE EAR INSERT HEARING AID 6 Sheets-Sheet 1 FiledDec. 50, 1957 ml l lz Feb. 7, 1961 H. M. BUSSE EAR INSERT HEARING AID 6Sheets-Sheet 2 Filed Dec. 50, 1957 zzvvewme. By Hra/d/Mflusse Qrromerzs1961 H. M. BUSSE 2,971,065

EAR INSERT HEARING AID Filed Dec. 50, 1957 6 Sheets-Sheet 3 Feb. 7, 1961Filed Dec. 30, 1957 Ill H. M. BUSSE EAR INSERT HEARING AID 6Sheets-Sheet 4 JiE-Jl.

AAAAA )ZZW,MJ%

Feb. 7, 1961 H. M. BUSSE EAR INSERT HEARING AID 6 Sheets-Sheet 5 FiledDec. 30, 1957 ArraA ZVJ Feb. 7, 1961 H. M. BUSSE 2,971,065

EAR INSERT HEARING AID Filed Dec. 30, 1957 6 Sheets-Sheet 6 ZFTVENTOR.

Unit

EAR INSERT HEARING AID Filed Dec. 30, 1957, Ser. No. 705,949

7 Claims. (Cl. 179-107) This application is a continuation-in-part of mvapplications Serial No. 615,189, filed October 10, 1956, now

abandoned, and Serial No. 634,368, filed January 15,

1957, now abandoned.

This invention relates to transistor amplifier hearing aids whereinelectric signals of a microphone are amplified by a transistor amplifierand supplied by it to an earphone or receiver held in the ear of theuser for enabling him to hear better.

Among the objects of the invention is a transistor amplifier hearing aidof the foregoing type in which all its elements, including themicrophone, receiver, transistor amplifier and the energizing batteryare combined in a submin'iature ear-insert unit which is small enough tobe confined in and fit within the outer ear cavity of the user, whereinthe earphone or receiver is eccentric relatively to the more outwardassembly, and which eliminates cords or sound-conducting tubes of thetype used in prior-art hearing aids.

Among the objects of the invention is such hearing aid insert unit smallenough to fit the outer ear cavity of the user and having at least onemovable element which enables the user to control the battery connectionto the amplifier, or the volume of the delivered sound, or both thebattery connections and the sound volume.

The foregoing and other objects of the invention will be best understoodfrom the following description of exemplifications thereof, referencebeing had to the following drawings, wherein:

Fig. l is an enlarged view of one form of an ear-insert transistorhearing-aid amplifier unit exemplifying the invention;

Fig. 2 is an enlarged exploded isometric view showing all parts of thehearing aid of Fig. 1;

Fig. 3 is an enlarged view of the back side of the amplifier chassis ofFig. 2, from the back side thereof;

Fig. 4 is a circuit diagram of the hearing aid of Figs. 1 to 3;

Fig. 5 is an exploded view similar to Fig. 2, of another form of hearingaid of the invention;

Fig. 6 is a circuit diagram of the hearing aid of Fig. 5;

Fig. 7 shows how an ear-insert hearing aid unit of the invention is heldin its operative position within the outer ear cavity of the user;

Fig. 8 is an elevational view of the hearing aid unit of Fig. 7;

Fig. 9 is a top view of the hearing aid unit of Fig. 8;

Fig. 10 is a partially exploded view of the chassis plate of Figs. 7-9,as seen from the bottom side of Fig. 8;

Fig. 11 is a circuit diagram of the hearing aid of Fig. 10;

Fig. 12 is a side view similar to Fig. 8, showing the opposite sidethereof;

Fig. 13 is a bottom view of the unit of Fig. 12;

Fig. 14 is a side elevational view similar to Fig. 8, with some of theparts in cross-section, of a modified form of ear-insert hearing aidunit of the invention;

Fig. 15 is an elevational view similar to Fig. 1, of the Zfl'iifitfiPatented Feb. 7, 1961 same ear-insert hearing aid unit, showing it inapproximately actual size; and

Fig. 16 is a bottom view of the same ear-insert hearing aid unit, asseen from the bottom side of Fig. 15.

Referring to Figs. 14, the hearing-aid insert unit 12 has an ear moldwhich is individually molded for each person. The ear mold 14 has aportion 16 that fits within the concha of the ear and a channel portion18 that extends into the ear canal. Channel or duct portion 18 has anoutlet opening 20 extending from, a wider cavity 22 having a smallerinterior cavity 24.

To the right of ear mold 114 is an outer casing 26, which surrounds theamplifier chassis 30, the battery cell 76, the microphone 89, andassociated elements. The assembly of Fig. 1 is adapted to fit within theouter ear cavity of the user with only the casing 26 being visible onthe front of the ear, and between casing 26 and ear mold 14 are mountedall of the transistor circuit elements, the sound-receiving andreproducing elements, as well as the source of power or battery, therebyenabling the user to carry the entire hearing aid at the ear and withoutconnections to other portions which would require the use of exteriorwire or cords.

The chassis disc or plate 30 (Fig. 2) is formed of electrical insulatingmaterial, its back side being shown in larger scale in Fig. 3. Theinsulating chassis plate 31 has printed conductors or a printedelectrical circuit, composed of conductive material printed or etchedthereon. Mounted on the surface of chassis disc 36* and connected to theprinted circuit are the electrical circuit components of the amplifier,shown in circuit diagram of Fig. 4. The operation of this circuit isconventional, and requires no further explanation. The amplifier hasthree transistors 34, 36 and 3S, five resistors 40, 42, 44, 46 and 48,and four capacitors 5h, 52, 54 and 56. On the opposite surface ofchassis disc 3%, as seen in Fig. 2, is mounted an insulating plate 58having a resistance 64 thereon which is connected to conductor 32, andengages a movable metallic wiper contact arm 62 which is also connectedto the amplifier circuit. A pair of circuit leads 6%, 66 extend fromchassis disc 34 and from its circuit to a double-pronged plug 68 (Fig.3) that is adapted to be inserted into an earphone or receiver which maybe embedded in the mold recess 22. The receiver 70 is of theconventional electromagnetic type and has a sound outlet projection orduct '72, which may be embedded in the smaller mold recess 24.

To the left of chassis disc 35 (Fig. 2) is secured a sheet metal batterycasing '74, providing a compartment housing a small disc-like battery'76. The battery casing 74- makes contact with one battery pole, and iselectrically connected to the printed circuit on chassis disc 36. Theother pole of battery '76 engages an electric contact 77 on chassis disc31 which is also connected to the printed circuit in the manner shown inFig.

To the right of chassis disc 30 (Fig. 2) is a microphone fill ofconventional electromagnetic design having a pair of electricalconductors 82, 84 extending therefrom, which are adapted to be suitablyjoined to the printed circuit. The microphone is embedded in orseparated from the other parts of the insert unit 12 by a layer ofsound-damping material 86, such as foam rubber or the like, which isdesigned to suppress transmission or feedback of sound vibrations fromthe receiver 70 to the microphone 80. Microphone 80 is enclosed on itsinward side by a metallic shield plate 88 of magnetic shield material ofhigh permeability. The shield plate 88 is covered with a layer ofelectric insulating material 86 for insulating it from printed circuit32 and other electrical components carried on the facing surface ofchassis disc 30. Alternatively, the microphone 80 may be enclosed in acasing of magnetic shield material which shields it from the magneticfield of receiver 70 and vice versa.

. The hearing aid is assembled as follows: The several transistors,resistors, capacitors, and switch and volume control, are mounted on thechassis plate 30 and are con nected with its printed circuit in themanner shown in Fig.v 4. The microphone 80 with its plate 88 and theunderlying sound insulating layer 86 is then secured to chassis disc 30,as by a pair of rivets 92. The ear mold 14, which may be individuallymolded to conform to the shapeof the ear cavity of the user, has seatedtherein the receiver 7%) which may form an integral part of the mold 14,or may be secured by cement or a bracket, not shown, to the chassis disc3%). The battery holder '74 may be secured to the chassis disc 30 by oneor more rivets 96, or it may be secured to the ear mold 114 by cement orscrews, not shown. The outer casing 26 is made of thin sheet materialand is retained in assembled position by screws or rivets 100 passingthrough casing holes 98 and secured to the lateral flanges of themetallic microphone mounting plate 88 in the manner seen in Fig, 1. Asmall opening in the outer casing 26, not shown, permits sound topropagate to the microphone 81).

Fig. shows how the ear-insert hearing aid unit 12 of the inventiondescribed above, in connection with Fig. 1, may be modified to providecertain additional features including a circuit switch which disconnectsthe battery, a control of the sound volume by theuser of the hearingaid, and means for readily removing the battery for replacement thereof.Where the same parts are used in both the hearing aid of Figs. 1-4 andthat of Fig. 5, they have similar reference numerals.

In Fig. 5, the chassis disc 30 is relatively movable, and has on itsopposite surfaces printed or etched circuits (not shown) of'the typedisclosed in Fig. 3, which connect a similar group of electricalcomponents of transistor amplifier hearing aid shown in circuit diagramof Fig. 6. Battery 76 engages chassis contact 77 and its other poleengages metallic battery cover section 118 which contacts the printedcircuit by a rivet or pin 119.

The hearing aid shown in the exploded view of Fig. 5 and in the circuitdiagram of Fig. 6, has a chassis disc 30' with printed circuits on itsopposite surfaces facing the ear mold 141 and the microphone 80'respectively, as in the unit of Figs. 1-3. To the printed circuitelements on the right surface of the chassis disc 30' facing themicrophone 80 (as seen in Fig. 5) with its printed circuit, areinterconnected the transistors 34', 36', 38, the four resistors 40', 42,44', and 46, the resistor 48' which is connected between capacitor 56'and battery switch elements 104, 108, and the four capacitors 5th, 52',54', 56', in accordance with the circuit diagram of Fig. 6. On theopposite left surface of the chassis disc 30' is pivotally mounted ametallic switch arm 104 which is biased to keep the battery circuitclosed by engaging with its outer end a stationary switch contact 108 ofthe chassis disc. The left side of chassis disc has also afiixed theretotwo stiff projecting metallic pins 110, 112 connected with the printedcircuit and arranged to engage, hold, and make metallic circuitconnections with the receiver 70' held positioned between the chassisdisc 30 and the ear mold 14. The receiver pins 110, 112 performfunctions similar to the receiver conductors 64, 66 and plug 68 of thehearing aid insert unit of Fig. 3. As in the unit of Figs. 1-3, thereceiver 70 is held in a position eccentric relative to the widerchassis assembly which fits the more outward part of the ear cavity.When the receiver 70' rotates with the chassis 30', they may be mountedconcentrically.

The left surface of the chassis disc 30' also carries :along its surfacean arcuate rheostat element 120 and a to be secured, battery andrheostat cover sections 118, 116, respectively. Rheostat cover section116 has an arcuate slot 132 substantially coextensive with the arcuaterheostat 120 of the chassis disc 30'. A relatively stationary controllever or member 126 is positioned between the rhecstat cover 116 andchassis disc 30. Control member 126 has a pivot pin 128 on which ispivotally seated the pivot hole 133 of the rheostat cover section 116 sothat when the latter is secured to the chassis disc 311', it may berotated around the stationary control member pin 12$. Control member 126has a lateral retainer projection 139 passing through arcuate slot 132of rheostat cover section 116 and seated and affixed in an opening 134of the ear mold 14' for holding it stationary and afiixed to the earmold 14 while the chassis 30 and other parts carried thereby are rotatedaround the fixed control-member pivot pin 128.

'Control member 126 carries an angular cam 138 with a cam surface shapedso that when the chassis disc 39 is rotated in clockwise directionaround pivot 128 (as seen on the left chassis side in Fig. 5), thecorner portion of cam 138 engages switch arm 104 and moves it from itsbiased, closed position to open position. In the further clockwisemovement of chassis disc 30, the upper region of control arm cam 138engages and pushes the adjacent edge of battery 76', under the batterycover 118, in a laterally outward direction, whereupon the exposed outeredge of the battery 76' may be gripped by the users fingers for removingor replacing it in the amplifier.

The rheostat and battery cover sections 116, 118, respectively, aresuitably affixed in their aligned position shown, to the adjacentchassis disc 30' for instance by rivet pins, not shown, extendingthrough aligned holes, also not shown, provided in them. The microphonewith its sound-attenuating layer 86 and its magnetic shield 88, aresecured to the right side of the amplifier chassis disc 30' (as seen inFig. 5), together with their surrounding casing 26, in the same manneras in the hearing aid unit of Figs. L3. The earphone 71) may be affixedto the chassis 311 as by securing it with a mounting ring 140 havingmounting ears with holes by which it may be secured to the chassis 30',as by the same rivets, not shown, with which the rheostat and batterycover sections 116, 118 are secured thereto. With such arrangement, theearphone 70 will rotate with the chassis plate around control memberpivot 128 when adjusting the volume control of rheostat and/ or openingthe switch 194, and/or ejecting the battery when the chassis 30' isturned by the users grip on the chassis casing 26 exposed along theexterior of the outer ear cavity. However, the earphone 70' may besecured, as by cement, to and made a stationary part of the ear mold14', in which case the earphone coil may be connected by flexible leads,such as indicated at 64, 66 in the unit of Figs. 1-3, to the printedcircuit earphone terminals 110, 112 of the chassis disc 30'.

In the ear-insert hearing aid unit shown in the exploded view of Fig. 5,and in the circuit diagram of Fig. 6, rotary movement imparted to thechassis disc 30 by turning its outer casing 26', will cause the pointedcentral part of the control arm cam 138 to first open battery switch 104and thereafter the cam 138 will cause the battery 76' to be nudgedupwardly as seen in Fig. 5, from its battery holder compartment topermit grasping the battery by the finger tips of the user for removaland/or replacement thereof. From the hearing aid unit described inconnection with Figs. 14, the ear-insert hearing aid unit of Figs. 5 and6 differs by the rotatable arrangement of the parts which are afiixed tothe outer casing 26 which may be gripped by the user along the exteriorof the ear, whereby the outer casing 26' together with the otherelements secured to the chassis disc Bil including the battery switcharm 104 and rheostat 120,

may be moved relatively to the relatively fixed parts held in the ear ofthe user, such as the ear insert with or without the earphone securedthereto, for adjusting the volume of the sound and/or cutting off theamplifier without removing any part of the hearing aid from its positionwithin the ear of the user. This arrangement thus permits the user toreadily adjust the volume of sound or to open the battery circuit whenhe prefers silence, thereby also saving on battery usage. It alsofacilitates easy replacement of the battery when it is worn out.

In the hearing aid amplifier of the invention, all components arecombined into a subminiature ear insert of lateral dimensions smallenough so that a large or major part, including the receiver,transistors, amplifier, microphone elements and other parts thereof, maybe held and confined within the outer ear cavity or concha of a humanear, such as shown in Fig. 7. As shown in Fig. 7, in accordance with theinvention, the components including the microphone, transistor amplifierelements, and the receiver, are assembled and combined into a unitaryhearing aid having its lateral dimensions suificiently small so as tofit within the concha cavity of the outer ear between the anti-helix andtragus thereof, with the receiver having a sound outlet duct connectedthrough a flexible ear tip fitting within and acoustically sealing theear canal Mil of the user.

Another form of such hearing aid is shown in Figs. 8 to 13. Referring tothe exploded and diagrammatic view of Figs. 10 and 11, it comprises anelectromagnetic microphone 111:: as in Figs. 14, the output of which isimpressed on an amplifier operating with three transistors 112a, 113a,114a, which also deliver the amplifier output to electromagneticreceiver 115a, as in Figs. 1-4. The circuits of all three transistorstages are energized from the same battery 117a. The output of themicrophone 111a is delivered through by-pass capacitor 121a and lead125a to the base and emitter of the first transistor 112a. The outputdeveloped between the emitter and collector of the first transistor 132ais delivered through by-pass capacitor 127a to the base and emitter ofsecond transistor 1131a. The output developed across the emitter andcollector of second transistor 113a is impressed upon a volume controlresistance 131a. he output developed at the tap 13241 of volume controlresistance 131a is delivered through by-pass capacitor 136a to the baseand emitter of the third power stage transistor 114a. The outputdeveloped across the emitter and collector of the power stage transistor114a is delivered to the coil of the receiver 115a. The emitters of allthree transistors are connected to a common supply lead 339a of battery117a. The collectors of the three transistors are connected to theopposite pole of the battery 1170 through resistor 1354:, volume controlresistor 131a, and the re-' sistance of the coil receiver 115a,respectively. Proper bias and operating connections are provided bycircuits including resistors 136a, 137a and 1380.

In accordance with the invention, the foregoing components of thetransistor amplifier hearing aid are combined into a compactamplifier-microphone unit 140a having lateral dimensions which fitwithin the outwardly opening concha cavity of the human ear between theanti-helix and tragus bordering the sides of the ear cavity, with thereceiver 125a extending eccentrically inwardly away from the wideramplifier-microphone unit 149a, and having at most half of itscross-sectional area, so that its sound outlet duct opens and transmitssound directly into the ear canal 169 while the microphone 111a isexposed on the outer side of the amplifier-microphone unit 140a. Asshown in Fig. 7, an ear canal insert 113a of flexible material held onsound outlet duct 191: of receiver ear insert 118a, fits against thewalls of the ear canal 160 and forms therewith an acoustic seal forsuppressing feedback of sound from the ear canal 169 towards themicrophone 111a positioned along the outer wall of the unit 140a.

As shown in Fig. 10, the microphone 111a and the receiver a. each haveelectromagnetic transducer structures wherein a ferromagnetic core andwindings interlinked with the core along a respective magnetictransducer axis of a winding-core section thereof operates to transduceacoustic or sonic signals into electric signals and vice versa.Furthermore, the magnetic transducer axis of the microphone 111a extendstransversely to the magnetic transducer axis of the receiver, therebymaterially reducing the magnetic linkage between them and serving tokeep the over-all feedback from the receiver 115a to the microphone 111abelow the level sufficient to start disturbing sustained feedbackoscillations and receiver whistling.

The ear canal insert 11812 has a sound outlet passage 1184:; into whichopens the sound passage 1194a of the sound outlet nipple 119a of thereceiver ear insert 2118:: (Figs. 7, 12, 13). The flexible sound outletear insert 118a may be made of any of the known synthetic, elastic,rubber-like resin materials. The wider ear insert portion may be formedof a materially stiffer material than its outward narrower end, whichshould be sufiiciently flexible so as to adjust itself to differentdirectional shapes of the ear canal 160.

The circuit components of the hearing aid unit are positioned andassembled along a support chassis plate 141 which forms part of aprinted circuit (Fig. 10). Support chassis plate 141 may be made ofconventional, strong and electrically insulating material having affixedthereto or therein printed metallic circuit portions of the amplifiercircuit. One set of these print-ed metallic circuit elements 142, 143,144, 145, 146, 14", 148 and 149, is exposed along the downwardly facingsurface of the chassis plate 141 (Fig. 12). The other set of printedmetallic circuit elements 151, 152, 153 and 154, is exposed along theupwardly facing surface of the insulating chassis plate 141 (Fig. 12).The rectangular microphone little is positioned along the upwardlyfacing surface of the chassis plate 141 so that its outer microphonewall lllrla picks up sound through openings Ill-2a for generatingcorresponding electric signals as in the device of Figs. 1-3. Themicrophone 111a is enclosed in a casing of magnetic shielding sheetmaterial to suppress interlinkage thereof with the receiver 115a bytheir stray magnetic fields.

Along one border region of the outward chassis surface are positionedtransistors 112a and 114a, resistance elements 136a and Kids, andcapacitor 133a. Along the opposite border region of this chassis surfaceare positioned transistor 113a, capacitors 121a and 127a, and resistorsa and 137a. As indicated in diagrammatic Fig. 10, the three wire ends oftransistor 112a pass through openings in and are soldered to printedcircuit portions 145, 14-7 and 144 of chassis plate 141. The wire leadends of transistor 114 are similarly joined to printed chassis circuitelements 14-4, 143 and 149. The two wire ends of resistor 133:: aresimilarly joined to printed chassis circuit elements 143, 149, to whichthe wire lead ends are joined as by soldering. The wire ends of resistor136a are similarly joined to printed chassis elements 145, 147. The twoleads of capacitor 13311 are similarly joined to printed chassis circuitelements 148, 152.

Transistors 113a, capacitors 121a and 127a, and resistors 135a and 137ahave their respective wire ends similarly joined to their associatedprinted chassis circuit elements and other circuit components, asindicated in wiring diagram of Fig. 10.

Printed chassis element 154 overlaps the printed circuit portion 149 onthe other side of chassis 141 and is joined thereto by a wire or moltensolder in a chassis perforation. In a similar way, other printed circuitelements are joined to proper overlapping printed chassis portions onthe opposite chassis side. Two stiff conductors 146%, 154-2 pass throughchassis 141 and are soldered to printed circuit portions 146, 154 sothat they and its electromagnetic microphone 111.

project in downward direction, as seen in Fig. 10, for makingconnections from the amplifier circuit to the receiver 115a.

Arcuate volume control rheostat 131a is positioned on the downward sideof chassis 141 and it has a pivoting contact arm 132a for varying thevolume of the sound output.

The small flat battery 117a is detachably held on the inward side ofchassis 141 by an overlying, bendable, springy stitf battery cover 161of spring metal, having one end suitably secured, as by rivets 162, tothe chassis 141. The battery cover arm 161 is electrically connectedthrough one of its connecting rivets 162 to printed chassis portion 153and connects thereto one flat terminal of battery 117a. The oppositeflat terminal battery 117a is held pressed against battery terminalportion 144-1 of the printed chassis circuit 144.

The springy battery cover 161 provides a nesting space for the battery117a. By gripping and flexing the free end of battery cover 161, thebattery 117a is released for removal or replacing it.

On the inward side of chassis plate 141 is eccentrically mounted themuch narrower inwardly projecting receiver 115a so that its center iseccentrically positioned relatively to the center of the amplifierassembly or unit 140 The receiver 115a may be held mounted in itseccentric position on the chassis 141, for instance, through engagementof its terminal sleeves (not shown), with terminal pins 154-2, 146-2 ofchassis 141. The receiver 115a may also be held in its eccentricposition on the chassis 141 by making the casing of receiver 115a aprotruding part of the wider inner casing wall 171, which is suitablysecured to chassis 141, as by securing ear projections to the edge ofchassis plate 141 with screws or cement. The inward casing wall 171 isformed of thin sheet metal and has a casing rim portion 172 engaging theperipheral edge of the amplifier chassis plate 141 which is suitablysecured thereto.

Battery cover 161 is positioned in an opening 171-1 of easing wall 171along which the battery cover 161 is exposed. Casing opening 171-1permits gripping and flexing of battery cover edge 161-1 for releasingthe battery 117a from chassis 141. Casing rim 172 has also an opening172-4 (Fig. 12) for actuating rheostat arm 132a and adjusting the soundoutput.

The outer side of chassis 141 holding microphone 111a and other circuitparts of the amplifier is enclosed by outer casing 181 which is secured,as by screws to the rim of inner casing 171 for enclosing the hearingaid assembly.

The outer casing 181 may have opening 181-1 for exposing outer casingwall 111-1a of microphone 111a. A relatively thick layer 183 of soundvibration attenuating material, such as sponge rubber, is placed betweenthe microphone 111a and the adjoining parts of the hearing aid, andparticularly its receiver 115a, for suppressing transmission or feedbackof disturbing vibrations and sound from the receiver to the microphonethat would set upwhistling sound generation.

Alternatively, outer casing wall 181 may extend over microphone 111a andhave openings through which propagated sound is transmitted to themicrophone 111a. In such case, the microphone 111a is held separated infloating condition from the overlying casing wall 181, for instance, bya border of sound-attenuating sponge rubber or the like.

The structure of the hearing aid shown in Figs. 7-13 may be readilydesigned so that the casing side walls are of D-shape conforming to theshape of the concha.

Figs. 14-16 show how the unitary ear-insert hearing aid described abovein connection with Figs. 7-13, may be modified in the manner explainedin connection with the hearing aid unit of Figs. and 6, so that rotationof Iitswider outer amplifier sections relatively to its inwardeccentrically mounted receiver imparts a control motion to internalcontrol elements for adjusting the volume of the sound output of thehearing aid unit and/or for selectively controlling the energization ofits amplifier circuit by the battery, in the manner explained inconnection with the hearing aid unit described above in connection withFigs. 5 and 6. The ear-insert hearing aid unit of Figs. 14-16 comprisesan outer wider microphone-amplifier unit 210 and an inward receiver unit215 positioned eccentrically relatively to the amplifier unit 210 andhaving a lateral cross-sectional area at most about one-half the lateralcross-sectional area of the amplifier unit 211). Themicrophone-amplifier unit 210 and the inward receiver unit 215 embodyand consist of substantially the same elements as the correspondingwider outer amplifier unit 140 and the inward receiver a of Figs. 7-13,or as the corresponding outer amplifier unit housed in casing 26' andthe inward receiver unit 70' of the instrument of Figs. 5 and 6. Thereceiver 215 is provided with a relatively long protruding sound outlet'duct 217 having an interior sound passage through which sound producedin the receiver is transmitted to the ear canal of the user. An earcanal insert 218, similar to the ear canal insert 118a of Figs. 7-13, isseated over and in tight coupling engagement with the threaded outersurface of sound outlet duct 217 of the receiver 215. The ear canalinsert 218 is shaped to fit with its flexible exterior against the wallsof the ear canal of the user so as to form therewith an acoustic sealwhich suppresses feedback of sound from the receiver sound outlet duct217 toward the microphone positioned behind the outer casing wall 210-1of the outer microphone-amplifier unit 210.

The casing of the eccentrically positioned receiver 215 has a relativelyrigid pivot arm 221 which is pivotally mounted on a pivot pin 222 withwhich it is pivotally secured to an inwardly protruding wall section 223of the inner casing wall 224 of the outer microphoneamplifier unit 210.The casing of receiver 215 and its pivot arm 221 are of metal and oneend of the receiver winding is electrically connected to the receivercasing and its metallic pivot arm 221 and therethrough to the metalliccasing of amplifier unit 210, corresponding to the connection ofreceiver 115a of Fig. 11 to the negative terminal of battery 117a. Thepivot pin 222 of the receiver pivot arm 221 is likewise of metal and it,together with its two metallic clamping heads 225, are electricallyinsulated from the metallic receiver pivot arm 221 and the metalliccasing wall 223 of the amplifier unit 210, as by an insulating sleeve226 surrounding the metallic pivot pin 222 and two insulating washers227 interposed between the metallic heads 225 of the pivot pin 222 andthe underlying metal portions of the receiver pivot arm 221 and casingwall 223. The other end of the receiver coil that is not connected tothe receiver casing and its pivot arm 221, is connected through aninsulated conductor 223 to the pivot pin 222. A

contact spring arm 231 having one end secured as by a rivet to ametallic circuit portion of printed circuit chassis plate 141, has itsfree end contact portion 232 biased into contact engagement with theadjacent pivot pin head 225, thereby completing the connection of thewinding of receiver 215 to the amplifier circuit, for instance, tothecollector of transistor 114a of the amplifier of the circuit diagram ofFig. 11.

The pivot pin 222 is arranged to permit pivotal movement of the casingof the microphone-amplifier unit 210 relatively to the eccentricreceiver 215 when it is held fixed in sealing engagement with the earcanal of the user, as described above. The printed circuit amplifierchassis plate 141 is provided with an arcuate rheostat element 131a anda cooperating pivotally mounted rheostat arm 132a pivotally mounted onthe chassis plate as by a pivot pin 243, for adjusting the amplifiergain in themanner explained, for instance, in connection with thecircuit diagram of Fig. 11 or Fig. 6.

The rheostat arm 132a is moved along its rheostat 131a by the controlmotion of a control rod 245 extending from the receiver 215 through anarcuate slot 246 of the amplifier casing wall 224 into couplingengagement with a coupling portion of the rheostat arm 132a. The controlrod 24-5 is relatively rigid, and is formed of insulating material suchas nylon, or it has an exterior insulating coating, so that it providesonly a mechanical motion-transmitting link between the receiver 215 andthe rheostat control arm 132a, without making any electrical connectionsbetween them. With this arrangement, a casing wall portion of themicrophoneamplifier unit 210 exposed along the open side of the widerear cavity, may be gripped by fingers of the user and rotated on pivot222 relatively to the fixed control rod 245 of the fixed receiver 215for imparting to the rheostat arm 132a a control motion which adjuststhe gain of the amplifier and the sound output of the receiver 215 inthe same manner as explained above in connection with the embodiments ofFigs. 8-13, Figs. 1-4, and Figs. 5 and 6.

The amplifier of the hearing aid units of Figs. 14-16 may have anamplifier circuit such as described in connection with Fig. 6, or withFig. 11, with the amplifier circuit including an energizing switch 11Mcooperating with a fixed switch contact, not shown but similar to 108,such as shown in Fig. 6, for selectively energizing or deenergizing theamplifier circuit by pivotal motion of the switch arm 104. The movableswitch arm 104' and its stationary contact are suitably mounted on theprinted-circuit chassis plate 141' of Figs. 14-16 in the mannerdescribed in connection with the corresponding elements of the hearindaid unit of Figs. 5 and 6, wherein the movable switch arm 104' isbiased, as by spring action, to a closed circuit position. A portion ofthe switch arm 104' is arranged to come in engagement with the fixedinsulating control pin 245 of the receiver 215 near the end of thepivotal volume-reducing movement of the amplifier unit 210 so that atthe end portion of this volume-reducing movement, the receiver controlpin 245 comes into engagement with energizing switch arm 104 for movingit to the circuit opening position in which the battery 276 isdisconnected from the transistor-amplifier circuit. With thisarrangement, and assuming that the casing of the amplifier unit 210 isin a position in which the energizing switch 104' is retained in itsopen position, the initial part of the rotary movement imparted by thefingers of the user to an exposed casing portion of themicrophone-amplifier unit 210 in a gain-increasing direction, will firstrelease the amplifier energizing switch 104 to its energizing positionin which it makes contact with its fixed switch contact and energizesthe transistor amplifier. Further movement of the amplifier unit 210 inthe same gain-increasing direction will cause the receiver control rod245 to move the rheostat control arm 132a over its rheostat element 131afor adjustably increasing the gain of the amplifier and the sound outputof the receiver to the level desired by the user. A similar oppositegain-decreasing rotary movement imparted by the finger of the user, toan exposed casing wall portion of the microphone-amplifier unit 210,will cause the receiver control rod 24-5 to move the rheostat controlarm 132a in opposite direction for adjustably reducing the gain andsound output of the amplifier, the end portion of this gain-reducingmovement causing the receiver control rod 245 to bring switch arm 104from the closed-circuit position to the open-circuit position in whichthe battery cell 276 is disconnected from the arm plifier circuit, asexplained in connection with Figs. 5 and 6. Otherwise, the ear inserthearing aid unit described above in connection with Figs. 14-16, mayhave the same construction as the ear insert hearing aid unit of Figs.8-13, or Figs. 5 and 6, or 1-4.

It will be apparent to those skilled in the art that the novelprinciples of the invention disclosed herein in connection with specificexemplifications thereof, will suggest various other modifications andapplications of the same. It is accordingly desired that in construingthe breadth of the appended claims, they shall not be limited to thespecific exemplifications of the invention described above. I

i I claim:

1. In a hearing aid device, an inward housing section with a soundoutlet duct projecting inwardly toward the users ear canal and anoutward housing section joined to and extending from the outward side ofsaid inward housing section and being opposite said sound outlet duct,said inward housing section having a lateral cross-sectional areamaterially smaller than said outward housing section and said twohousing sections forming together an integral unit having laterallydimensions fitting the outer ear cavity between the anti-helix, tragusand anti tragus, said inward housing section having mounted therein areceiver comprising an electromagnetic acoustic transducer having asound outlet space connected to said outlet duct, said outward housingsection having mounted therein a battery cell, a microphone with anelectromagnetic transducer exposed to exterior sound and transistoramplifier means electrically connected to said cell between thetransducers of said microphone and said receiver for supplying to saidreceiver amplified microphone signals, each of said electromagnetictransducers comprising a ferromagnetic core and windings interlinkedwith said core along a winding-core secton and transducing axis thereof,the winding-core section of said receiver being laterally displaced inan eccentric position relatively to the winding-core section of saidmicrophone, a magnetic shield element of magnetic sheet metal interposedbetween the core and winding of the microphone and receiver transducers,said receiver having a transducing axis extending transversely to thetransducer axis of said microphone for suppressing in conjunction withsaid shield element magnetic signal feedback from the receivertransducer to the microphone transducer and maintaining the over-allfeedback between them below a level sufficient to start sustainedelectric feedback oscillations and whistling.

2. In a hearing aid device having dimensions fitting within a usersouter ear cavity between its anti-helix, tragus and anti-tragus, aninward housing section and an outward housing section including anoutside wall, said two housing sections mechanically joined in aside-to-side relationship in which said outward section is rotatablewith respect to said inward section, a receiver mounted within saidinward housing section and directed toward the users ear canal through asound outlet duct, an interior space between said inward housing sectionand the outside wall of said outward housing section, said interiorspace having mounted therein a battery cell, a transistor amplifierhaving at least two tran sistors and a microphone exposed to exteriorsound, said battery cell electrically connected to said amplifier whichis electrically connected between said receiver and said microphone,said amplifier including amplifier current control means having amovable control element mechanically coupled to said inward housingsection and moved by relative rotation between said inward and outwardhousing sections.

3. In a hearing aid device as claimed in claim 2, said receiver and saidmicrophone are electro-magnetic and have axes eccentric with respect toeach other.

4. in a hearing aid device as claimed in claim 3, a magnetic shieldelement interposed between said receiver and said microphone.

5. In a hearing aid device as claimed in claim 2, said current controlmeans including volume control means and an open-close circuit switchbetween said battery cell and said transistor amplifier, said switchmovable control element having a volume control range 10 of movement andtwo separate ranges of movement outside its volume control range ofmovement, the first separate range of movement operates an open-closecircuit switch between said battery cell and said transistor amplifierand the second separate range of movement ejects said battery cell fromsaid outward housing section in which said battery cell is movablymounted.

References Cited in the file of this patent UNITED STATES PATENTS2,485,405 Olney et a1. Oct. 18, 1949 2,787,670 Rowland Apr. 2, 19572,882,348 Erickson Apr. 14, 1959 FOREIGN PATENTS 541,987 Italy Apr. 12,1956

